2005 Yamaha G28-AA "UMAX MEDIUM DUTY II" (CARB) Service a...
The G28 cars are the medium-duty half of the UMAX range, and the 2005 G28-AA, code G28AA, shares its service manual with the light-duty machines. That manual is LIT-19616-G2-70.
Yamaha's coverage here begins in 2004 and ends in 2009. Alongside the other G28 UMAX MEDIUM DUTY II variants, the book addresses the carbureted G27-AC, G27-AE, G27-AF and G27-AZ and the 48-volt DC-motor G27-EC through G27-EZ cars. Where a medium-duty component differs from its light-duty equivalent, the procedure says which car it applies to.
Expect the factory's full service treatment: engine and transmission work, brake adjustment and overhaul, steering and suspension, electrical diagnosis with wiring diagrams, plus torque and clearance specifications throughout. Confirm the code on the frame plate reads G28AA and this is the right reference.